misleading fix-it with `bugprone-unintended-char-ostream-output` in templated code

[firewave]

The fix-it is problematic if it is a templated type and should probably be omitted in that case:

#include <cstdint>
#include <sstream>

template<typename T>
void func(const T& data)
{
    std::ostringstream ostr;
    ostr << data;
}

void f()
{
    func((char)0);
    func((int8_t)0);
    func("");
}

<source>:8:10: warning: 'signed char' passed to 'operator<<' outputs as character instead of integer. cast to 'unsigned int' to print numeric value or cast to 'char' to print as character [bugprone-unintended-char-ostream-output]
    8 |     ostr << data;
      |          ^  ~~~~
      |             static_cast<int>(data)

https://godbolt.org/z/93axK1E4M

Originally posted by @firewave in #127720 (comment)

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Oliver Stöneberg (firewave)

The fix-it is problematic if it is a templated type and should probably be omitted in that case: ```cpp #include <cstdint> #include <sstream>

template<typename T>
void func(const T& data)
{
std::ostringstream ostr;
ostr << data;
}

void f()
{
func((char)0);
func((int8_t)0);
func("");
}

<source>:8:10: warning: 'signed char' passed to 'operator<<' outputs as character instead of integer. cast to 'unsigned int' to print numeric value or cast to 'char' to print as character [bugprone-unintended-char-ostream-output]
8 | ostr << data;
| ^ ~~~~
| static_cast<int>(data)

https://godbolt.org/z/93axK1E4M

_Originally posted by @<!-- -->firewave in https://github.com/llvm/llvm-project/issues/127720#issuecomment-2729734197_
            
</details>

[firewave]

CC @HerrCai0907